It has previously been proposed that the pane of soda glass should be covered, where it is held by the retaining strip, with a masking strip, specifically a metal listel, fastened to the glass or to the device that holds it by an adhesive that loses its adhesion when hot. A solder with a low melting point is an example of the kind of adhesive that might be used. Such a construction is disclosed in copending application "Fire-Proof Window", filed Dec. 5, 1977, Ser. No. 857,417, and assigned to the assignee of the present application.
The suggested application of masking strips or listels to the glass in the region of the device, such as a cushion frame, that holds it means that the window will look like a window of ordinary frame construction without impairment of its resistance to fire to any extent. The exposed borders of the pane of glass are thus masked and only uncovered in the event of a fire. The use of such listels is appealing on both aesthetic and practical grounds, especially when the devices that hold the pane of glass in the frame are made of a perforated cushion frame.